You upgraded via RomTool? If so it replaced the Rom you are running 1.20 software but there are a couple things that are changed during the update process besides the Rom. First is the radio firmware (I am guessing you have 1.51 not 1.71) and the software and version tokens. You can use the Rom Tool to change the tokens. I would use the RomTool to change the tokens and then run the official updater once. Then apply your custom Rom again.